The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-284067 filed on Sep. 18, 2001 the entire contents thereof is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a water jet propulsion apparatus for use in a boat. Particularly, the invention relates to a bearing structure of an impeller shaft for supporting an impeller of the water jet propulsion apparatus.
2. Description of Background Art
A known conventional water jet propulsion apparatus is as shown in FIG. 5 (Japanese Utility Model Registration No. 2,548,210).
The water jet propulsion apparatus is attached to the rear portion of a boat body and has a stator (duct) 1 forming a channel, an impeller 2 is rotatably disposed in the stator 1, and an impeller shaft 3 is rotatably supported by bearing members 4 and 5 provided in the front and rear part of a bearing 1a disposed in the stator 1 and coupled to the rear part of the impeller 2.
A drive shaft 6 is coupled to the front part of the impeller 2. When the drive shaft 6 is driven by a not-illustrated engine, the impeller 2 is rotated and a water stream is jetted rearwardly in the direction R, thereby propelling the boat body forward F. A thrust force for pulling the impeller shaft 3 forward F acts on the impeller shaft 3.
As is obvious from the shape of the bearing 1a shown in the diagram, the bearing member 4 on the front side is assembled to the bearing 1a from the front and the bearing member 5 on the rear side is assembled to the bearing 1a from the rear, so that the thrust force acting on the impeller shaft 3 is received by the bearing member 5 on the rear side.
More specifically, a flange 3a formed in the rear part of the impeller shaft 3 is in contact with an inner race 5a of the bearing member 5 and an outer race 5b of the bearing member 5 is in contact with a step 1b of the bearing 1a, so that the thrust force can be received.
The above-described conventional water jet propulsion apparatus has a problems such that, since the bearing members 4 and 5 on the front and rear sides have the same size, the thrust force acting on the impeller shaft 3 cannot be received by a large bearing member.
An object of the present invention is to provide a water jet propulsion apparatus which can solve the above problem and receive a thrust force acting on the impeller shaft by a large bearing member.
To achieve this object, a water jet propulsion apparatus of present invention includes a stator forming a channel, an impeller rotatably disposed in the stator, and an impeller shaft rotatably supported by bearing members provided in front and rear parts of a bearing disposed in the stator and coupled to a rear part of the impeller. The bearing member mounted on the rear side which receives a thrust force of the impeller shaft is larger than the bearing member on the front side.
A water jet propulsion apparatus of the present invention includes the bearing members on the front and rear sides that are both assembled on the bearing from the rear.
The water jet propulsion apparatus of present invention includes a stator forming a channel, an impeller is rotatably disposed in the stator, and an impeller shaft is rotatably supported by bearing members provided in front and rear parts of a bearing disposed in the stator and coupled to a rear part of the impeller. The bearing member on the rear side which receives a thrust force of the impeller shaft is larger than the bearing member on the front side. Consequently, in the water jet propulsion apparatus, the thrust force acting on the impeller shaft can be received by the large bearing member on the rear side.
Also, the bearing member on the front side can be constructed to be smaller than the bearing member on the rear side, so that the size of the bearing of the stator supporting the bearing member does not increase to a great extent. As a result, the size of the water jet propulsion apparatus itself can be prevented from being increased.
As for the water jet propulsion apparatus of the present invention both of the bearing members on the front and rear sides are assembled on the bearing from the rear. Therefore, the following action and effect are obtained.
Since the conventional water jet propulsion apparatus has a configuration such that the bearing member 4 on the front side is assembled to the bearing 1a from the front, there is a problem wherein the workability at the time of assembly is very low. Since the impeller 2 is positioned in front of the bearing member 4 on the front side, the drive shaft 6 is coupled in front of the impeller 2 and, further, the engine exists in front of the drive shaft 6, the assembly workability of the bearing member 4 on the front side is very low and it is consequently difficult to perform maintenance.
In contrast, in the water jet propulsion apparatus of the present invention, both of the bearing members on the front and rear sides are assembled to the bearing from the rear, so that a remarkably improved assembly workability is provided as compared with the conventional technique. Accordingly, an effect of facilitated maintenance is also obtained.
In the configuration where both of the bearing members on the front and rear sides are assembled to the bearing from the rear as described above, if the bearing member on the front side is also a large bearing member like the bearing member on the rear side, the size of the bearing increases and, as a result, a problem results in that the size of the water jet propulsion apparatus also increases. However, in the water jet propulsion apparatus of the present invention, the bearing member on the front side can be constructed to be smaller than the bearing member on the rear side. Thus, the size of the bearing of the stator supporting the bearing member does not increase to a great extent and the size of the water jet propulsion apparatus itself can be consequently prevented from being increased.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.